Performance of the older adult may be accompanied by psychomotor deficits, particularly when changing environmental demands require rapid shifts in responding. But laboratory investigations of the nature and origin of these deficits often have been based on restricted observations of behavior. Thus questions remain about the limits of performance capability in the older person. The proposed research uses operant conditioning methods and concepts to compare performances of young and old adults under schedules in which complex response sequences must be learned and executed within limited periods of time. In line with an operant analysis, emphasis will be placed on observations of steady-state behavior of individual subjects using the repeated-acquisition-of-response-chains procedure as a baseline for study of variables which control speed and accuracy of performance. These variables include: length and complexity of the response chains; rates at which chains are paced; adjusting schedules in which response requirements change depending on speed of accuracy; addition and deletion of stimuli that cue correct response sequences; and differential reinforcement of errors of omission and commission. The generality and stability of changes also will be investigated by measuring transfer to more conventional procedures, e.g., paired-associate learning, and by conducting follow-up observations after training is completed. The long-term objectives are to identify areas of deficit in the older adult and to develop ways of restoring competent performance through manipulation of environmental contingencies of reinforcement.